<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=.dem, initial-scale=1.0">
    <title>JS学习&笔记</title>
    <script src="JS OOP学习.js"></script>
</head>
<body>
    <div id="demo">11</div>
    <button onclick="window.alert('hello!')">试一试</button><br>
    <script src="JS学习&笔记.js">
        // document.getElementById("demo").innerHTML= 1+4;
        // document.write(5+7);
        // console.log(1+1)
    </script>
</body>
</html>